Hitherto, silver paste has been mainly used to joint a semiconductor element with a semiconductor-element-mounting support member. However, the support member used has also been required to be made small-sized and minute as semiconductors have been made small-sized and the performance thereof has been made high in recent years. Silver paste has come not to meet such requirements by generating of the problem at the time of wire bonding resulting from the paste smudge and the inclination of semiconductor elements, control difficulty of the film thickness of an adhesive sheet, generating of voids in the adhesive sheet, and others. In recent years, therefore, a sheet-form adhesive has come to be used in order to meet the requirements.
This adhesive sheet is used in an individual-piece sticking mode or a wafer-back-face sticking mode. When the adhesive sheet in the former individual-piece sticking mode is used to produce a semiconductor, the semiconductor device is obtained by cutting or punching out a reel-form adhesive sheet into individual pieces, bonding one out of the individual pieces onto a support member, jointing a semiconductor element made, through a dicing step, into an individual piece onto the adhesive-sheet-bonded support member to form a semiconductor-element-jointed support member, and, if necessary, causing this member to undergo a wire bonding step, a sealing step and other steps. However, in order to use the adhesive sheet in the individual-piece sticking mode, it is necessary to use an exclusive fabricating device for cutting the adhesive sheet and then bonding the resultant onto the support member. Accordingly, there arises a problem that costs for the production are higher than those in the method using silver paste.
Meanwhile, when the adhesive sheet in the wafer-back-face sticking mode is used to produce a semiconductor device, the semiconductor device is obtained by sticking the adhesive sheet onto the back face of a semiconductor wafer, sticking a dicing tape onto the other face of the adhesive sheet, dicing the wafer into individual semiconductor elements, picking up one of the individual adhesive-sheet-bonded semiconductor elements, jointing it with a support member, and causing the resultant to undergo the steps of heating, curing, wire bonding and others. This adhesive sheet in the wafer-back-face sticking mode does not require any device for making an adhesive sheet into individual pieces since a semiconductor element with the adhesive sheet is jointed with a support member. Thus, a conventional fabricating device for silver paste can be used as it is, or the device can be used in the state that a part thereof is improved by, for example, the addition of a hot plate thereto. For this reason, attention is paid to the production method, as a method capable of making costs for the production relatively inexpensive, among fabricating methods using an adhesive sheet.
However, in the method using an adhesive sheet in the wafer-back-face sticking mode, it is necessary to conduct two sticking steps, wherein the adhesive sheet and a dicing tape are stuck, before the above-mentioned dicing step. For this reason, there has been a require for simplified working steps. Thus, suggested is a method of putting an adhesive sheet onto a dicing tape, and sticking the resultant on a wafer (for example, Japanese Patent Application Laid-Open Nos. 2002-226796, 2002-158276, and 2-32181).
In the method using an adhesive sheet in the wafer-back-face sticking mode, it is necessary to cut the adhesive sheet at the same time as a wafer is diced. However, in ordinary dicing methods using a diamond blade, it is necessary to make the cutting speed small in order to cut the wafer and the adhesive sheet simultaneously. Thus, costs increase.
In recent years, the following is suggested as a wafer-cutting method: a method of performing the step of making a wafer into a state that the wafer can easily be cut, such as the step of making trenches which will be cutting stripes in a wafer without being completely cut or the step of forming a modified regions by radiating a laser into a wafer along lines intended to be cut; and subsequently cutting the wafer by, for example, the application of external force thereto. The former is called half cut dicing, and the latter is called stealth dicing (for example, Japanese Patent Application Laid-Open Nos. 2002-192370 and 2003-338467). These methods have an advantageous effect of decreasing defects, such as chipping, when the thickness of a wafer is particularly small. Moreover, the methods require no calf width. Thus, according to the methods, yield-improving effect and other effects can be expected.
In order to perform a semiconductor device producing process according to the wafer-back-face sticking mode by use of the half cut dicing or stealth dicing, it is necessary to cut an adhesive sheet and a wafer simultaneously. However, when an ordinal adhesive sheet is used, it is difficult to cut the sheet at the same time as a wafer is cut. When a non-elastic adhesive sheet having a good breakability is used as the adhesive sheet, the adhesive sheet and a wafer can be simultaneously cut in the state that cutting faces of the two are made substantially consistent. However, the non-elastic adhesive sheet has a low fluidity; therefore, the sheet is not easily stuck onto the wafer at a low temperature of 100° C. or lower. Additionally, the adhesive sheet is cracked since the adhesive sheet itself is brittle. Thus, it is feared that adhesion reliability thereof deteriorates.